Paving machines are used to lay and level a paving material, such as asphalt, on a ground surface for the construction of roads, bridges, parking lots, and other such surfaces. In general, paving machines include a chassis, a hopper for storing the paving material, an auger that distributes the paving material on a ground surface, and a screed assembly that compacts/levels the paving material to a desired mat thickness. The screed assembly may be rear-mounted on the paving machine behind the hopper, the chassis, and the auger relative to the direction of travel. The screed assembly may include a main screed and one or more extension screeds mounted behind (or in front of) the main screed. The extension screeds are laterally extendable from the main screed to adjust for varying ground surface widths. In addition, the main screed and the extension screeds may each include a bottom-facing screed plate that compacts the paving material on the ground surface at a pre-determined “angle of attack”. Some screed assembly designs may also include a tamper bar at the front of the main and/or extension screeds that move up and down vertically to pre-compact the paving material in front of the main and/or extension screeds.
While effective, uncompacted paving material may be prone to leak through a gap between the main screed and the extension screeds, when the extension screeds are fully-extended. This may ultimately lead to undesirable streaks of uncompacted paving material that trail behind the paving machine. This problem may be more prevalent with screed assembly designs having tamper bars because the tamper bars may push the paving material forward, causing it to bypass other systems designed to block paving material leakage between the main and extension screeds.
U.S. Pat. No. 6,106,192 addresses the problem of mat streaking in paving machines caused by overlapping edges of front-mounted extendible screeds a rear-mounted central main screed. In this case, the streaks are formed from compacted material that is more densely compressed and shinier than the rest of the mat. To prevent the formation of the shiny streaks, a flow-modifying device is disclosed that plows the paving material at the outer edges of the main screed toward the central axis of the main screed. However, the flow-modifying device disclosed therein does not address or correct the problem of streaks of uncompacted material caused by paving material leakage through gaps between the main and extension screeds. Moreover, the flow-modifying device is specifically designed for paving machines having front-mounted (not rear-mounted) extendible screeds.
There is a need for screed assembly designs that prevent the leakage of paving material between the main screed and rear-mounted extension screeds when the extension screeds are fully-extended.